The invention is concerned with a method and an apparatus for providing radio access bearer services in a network comprising a core network and a radio access network on radio access bearers between said networks. It is suitable for sending real-time services of different applications.
The operators, which administrate a telecommunications network can offer both complete telecommunications services or only bearer services. The bearer services are transport systems for the communication, whereas the telecommunications services also include functions for connection and rules for the communication.
A telecommunication service can be a basic service (as for example speech) or an application service (as for example an information data base) or an additional service (which can be a modified basic service). The telecommunication services are classified on the basis of the form they are presented in for the users, such as speech, data, video and multimedia.
Transparence is needed to send all these services through the network. A good transparence means that the delays through the coupling components in the network are minimized, that the information flow stays intact and that the bandwidth needed for the sending is available. The three most important parameters in connection with transparence are thus bandwidth, bit error and delay. The requirements on bandwidth for speech, video and data differ from each other. Video transmission e.g. sets special requirements on the networks, due to the maximal variation in delay allowed. For high quality video transmission it is required that the variations in delay are small, sometimes not more than a few milliseconds.
Different transfer modes, such as the circuit mode and the packet mode exist for transmission of the information of different services. In the circuit mode, the information is sent in time frames of given lengths. In the packet mode, the information is divided into packets with address headers for the transport through the network. It is more and more usual that the information sent changes transfer mode on the way through the network. The aim in the future is a transmission of different types of services in the same network independently of bandwidth and transfer mode.
The communication through the networks is carried out in accordance with certain agreed rules called protocols. TCP/IP is a set of protocols for packet mode used over the Internet, which is the world wide network connecting different computer networks in the whole world. The main task of the IP protocol is the addressing. The TCP protocol takes for instance care of the sequencing and flow control between the hosts.
In a communication there are two phases, the coupling and the session. In a telephone call, the conversation itself is the session. In other types of communication, the session phase is the phase during which data is transmitted between the users.
A telecommunications network is divided into the access network and the core network. The access network is the part connecting the subscriber and the local station, whereas the connections between the local stations define the core networks.
In a mobile telecommunications system, there are regularly positioned local base stations within a service area. Such an area is divided into cells with one base station for each cell. A mobile station within a radio access network communicates with the geographically closest local base station in the service area. Communication with the fixed core network thus takes place through the radio access network.
Cellular systems today are experiencing a tremendous increase. In the beginning of 90s, the major service for wireless users was speech. Speech is a real time, delay-sensitive service and the techniques used in cellular voice communication are in many aspects copied from the fixed telecommunication networks. Thus, the cellular systems are traditionally circuit-switched and communication channels across the radio interface are defined as dedicated channels.
However, recently other types of services have started to emerge in the cellular world. These are data services with rather varying requirements on the radio bearer in radio communication with respect to e.g. delay and bandwidth. The common denominator for such services is that they can take advantage of using the packet data based type of transmission.
Actually, that trend has also started on the fixed side with the tremendous growth of Internet in recent years. The TCP/IP protocol suite is the main platform for such packet data based infrastructure where different application services (communication services) are being run onto, including even voice. E-mail, Internet browsing and video conferencing are just examples of such new application services. IP is a packet mode service and offers xe2x80x9cbest effort deliveryxe2x80x9d meaning that the connection cannot be guaranteed.
Communication services between different systems can be used by means of applications. By using standardized applications, data can be changed in different systems in a simple way. The applications use TCP (The Transmission Control Protocol) or UDP (The User Datagram Protcol) as media. Examples of applications are SMTP (Simple Mail Transfer Protocol), SNMP (Simple Network Management Protocol), WHOIS (a catalogue database), NTP (Network Time Protocol), HTTP (Hyper Text Transfer Protocol) and WWW (a network of information databases). These applications are described more in detail in different RFC (Request for Comments) recommendations or they are specific for the actual service provider. The session traffic flows are of different lengths depending on application. In the future, there will be much more application services in form of voice, pictures, security etc.
Packet data based services provide opportunities to multiplex a number of users on the same communication channel and transmit information more efficiently (in terms of data throughput) than the circuit switched networks. A key feature of the radio interface is the possibility to transport multiple parallel services with different quality requirements on one connection.
Different applications sent across the interface between the core network and the radio access network require different radio access bearers for the service they provide. For packet data based services, there exists a number of attributes characterizing the radio access bearer services and a negotiation protocol across the interface between the core network and the radio access network. The performance of the application depends on these attributes for the bearer service, which may involve bandwidth, quality of service, peak bit rate, minimum bit rate etc.
Standardization of third generation mobile communication systems is now rapidly progressing in all major regions of the world. These systems, which are called IMT-2000 within ITU (International Telecommunications Union) and UMTS (Universal Mobile Telecommunications System) within ETSI (European Telecommunications Standards institute), will extend the services provided by current second generation systems, e.g. GSM, with high-rate data capabilities. The general system architecture of UMTS/IMT-2000 includes User Equipment (UE), UMTS Terrestrial Radio Access Network (UTRAN) and the Core Network. Furthermore, the general architecture includes two general interfaces of which the Iu interface is between UTRAN and the Core network and the Uu interface is between UTRAN and the user equipment.
The evolution of UMTS is just taking place and there is no finished concept on how the radio access bearer service negotiation should be performed across the Iu interface on basis of which the radio access bearers are granted. The concepts for evolving packet data based cellular solutions are also needed for other cellular systems like for example GPRS (General Packet Radio Services).
The radio access network part of the network provides radio access bearer services for the core network upon demand. Certain issues have to be taken into consideration, if packet data traffic is wished to cross the radio interface between the core network and the radio access network in a spectrum efficient way.
One problem in connection with using radio access bearer services offered for the core network is how to establish a radio access bearer needed for a certain application.
One mobile user can be granted one or more radio access bearer services, e.g. when running different applications in parallel or when a certain application requires different qualities of service for different streams. The conventional mobile subscription method does, for example, not take into consideration different application needs with respect to the attributes characterizing the bearers, and therefore there is a risk for either over- or under-dimensioned radio bearers when granting radio access bearer services (RABS) in for example UMTS.
In some types of cellular communication networks, a user defines his or her service requirements to a bearer (i.e., a service provider) in terms of one or more requested qulity-of-service (QoS) vectors or requested service vector, RSV. Each vector consists of a number of QoS parameters which relate to the required service. Alternatively, a user""s requirements may be input into a computer or a computer application which performs the negotiation with the bearer. The QoS parameters may include, but are not limited to, required bit rate (peak, mean and/or some other rate), required bit error rate (BER) and required transmission delay. In addition, the user may also specify a price parameter for a desired service. For a given application, a range of values for each of these QoS parameters may be acceptable to the user. For example, in a web browsing application, a user normally desires a high bit rate for which the user is willing to pay a higher price. However, a user may tolerate a lower bit rate if the user is interested in minimizing the price. For some applications, the range of values for certain QoS parameters that the user is willing to accept may be relatively small. For example, in a voice application, the user may not be willing to tolerate a lower bit rate or a longer transmission delay because of the susceptibility of speech data to low bit rates and/or long delays. Under less than acceptable conditions, e.g., low bit rate and long delay, it may be preferable that the call be blocked.
One way the user can express its service requirements to the service provider is to define two QoS vectors, wherein the QoS parameter values in the second QoS vector represent an acceptable (or minimum level of) service. Typically, the desired QoS parameter values indicate a lower price level sensitivity on behalf of the user, as suggested above. In contrast, the acceptable QoS parameter values are associated with a higher price sensitivity. In the case of speech, the desired value and the acceptable value for certain QoS parameters (e.g., maximum transmission delay) may be the same, thus indicating a user""s unwillingness to accept less than desired values for those QoS parameters. It is also possible to define a desired service, a minimum acceptable service and services therebetween.
At call set-up, handover and call re-negotiation, a determination has to be made as to which service will be used to establish a connection. The requirements of the user and the capability of the bearer have to be taken into account. The capability of the bearer can also be expressed in the form of QoS vector and may be referred to as an offered service vector, OSV. The procedure that results in generation of an OSV is called a bearer service generation. The procedure that attempts to match user requirements with bearer capabilities is called bearer service negotiation. The bearer service negotiation process results in the generation of a negotiated QoS vector or NSV. In general, a NSV contains QoS parameter values that reflect the service which the service provider is capable of providing and which satisfy requirements of the user specified values in a RSV. In the event that no match between the requirements of the user and the capability of the bearer is established, the NSV is said to be empty.
A service provider can not always guarantee the quality of service defined by the NSV. It is merely something the service provider will attempt to achieve. However, during the time period between the bearer service negotiation and, for example call-set-up, conditions may change due to such phenomena as data traffic fluctuation and fading, thereby making it impossible for the service provider to achieve the level of service defined by the NSV. If the service provider cannot achieve at least the minimum requirements, the bearer service has to be renegotiated, or in the case of an on-going call, handed over (i.e., to a different service provider) or dropped.
With data services being added to cellular networks, wireless systems engineering is faced with the task of having to accomodate connections belonging to different services each of which may have a different quality requirement. In a complex mixture of different applications using wireless access in second generation systems (such as GSM, TDMA/136 etc.) WCDMA and wireless LANs, lack of structured handling will result in a low system performance and create added difficulty to operators managing networks.
Full rate and half rate speech is currently available in commercial GSM systems and circuit switched data will soon extend to multiple slot transmission. Admission control (which controls access to a service) of these mixed services, though possible, is rudimentary since there are few service types. In addition, load of services other than full rate speech is load. Attempts to address mixed services wireless systems have focused on the task of allocating radio resources to a delay-critical service such as speech and a non-delay critical service such as data according to a predefined access control.
Several problems exist in current solutions for handling mixed services. These problems are treated on a service-by-service basis without an overall structure which leads to difficulties in a system supporting a complex mix of services.
For admission control, service differentiation and user differentiation are not covered extensively. That is, there may be resources available for one important user but not for another.
Adaptive applications, i.e. applications with multiple operation modes, are not well covered either. A video codec, for example, can operate in multiple bit rate modes. These modes correspond to the bandwidth available, and hence bandwidth negotiation has to take place at least at connection set-up.
Elastic applications, such as web browsing, which can operate in a single mode using a variety of bearers (and give the user a corresponding variety of quality) have also not been treated extensively.
In the international patent application WO 99/01991 by NOKIA TELE-COMMUNICATIONS OY, there is presented a method and an arrangement for supporting TCP/IP services in cellular radio access networks connected to a telecommunications network offering TCP/IP services. In accordance with the solution presented in this document, the bearer service parameters required by different TCP/IP services are predetermined in the radio access network, the correct parameters for a given connection being selected by identifying the TCP/IP service on the basis of the content of the first IP packet received. Thus, different TCP/IP services can be handled in a different way in the radio access network and a bearer service that best corresponds to the actual needs can be established through the radio access network by means of a local database.
There is, however, a need for faster and more flexible methods for granting the radio access bearer services, so that the IP packets could be sent on an optimal radio access bearer from the beginning of the sending.
What is also desired, is a solution for handling mixed services which is adaptive in order to accomodate applications having multiple operating modes as well as for handling elastic applications.
It should also be possible to change the radio access bearer during a session if the situation so require, since the time varying characteristics of the radio access network is a problem. The radio access network might for instance decrease (or increase) the offered bandwidth for individual users or a subset of users, due to e.g. change in traffic load or link budget, etc.
The object of the invention is a method and an apparatus for providing radio access bearer services in a network which solve one or more of the above mentioned problems.
Thus, one object of the invention is to achieve faster methods and apparatuses for establishing an optimal radio access bearer needed for a certain application.
A second object of the invention is to achieve methods and apparatuses for mapping of the data stream on the right radio access bearer.
A third object of the invention is to achieve methods and apparatuses for taking varying characteristics of the radio network into consideration.
The method of the invention for providing radio access bearer services of different applications in a network comprising a core network and a radio access network through radio access bearers between said networks, is mainly characterized by the steps of identifying one or more session traffic flows being sent by an application, characterizing the identified session in the form of parameters needed for the determination of one or radio access bearers, converting the characterized parameters into radio access bearer attributes, requesting and establishing one or more radio access bearers defined by means of said attributes, mapping each session on the correct radio access bearer established upon said request, indicating the end of a session and releasing the radio access bearer(s) when not needed anymore.
The apparatus of the invention of handling radio access bearer services of different applications in a network comprising a core network and a radio access network is a radio access bearer management node introduced in the network between said core network and radio access networks. It is mainly characterized by the means for carrying out the steps of the method of the invention.
In conclusion, the invention can provide a functional entity for example on the core network side in a network such as in UMTS or similar networks that handles the radio access bearer service negotiation process for the packet data traffic""s account. Knowledge/information of the actual session flows(s) of a packet stream for identifying and characterizing the session flows is used for determination of the number of radio access bearers needed, and assigning values to the radio access bearer attributes. The method also provides for a method for mapping the user data session flow(s) onto the established radio access bearers.
Sometimes de-multiplexing has to be used in order to extract different streams from the same source, e.g. video, voice and signaling in order to map the right traffic on the right bearer.
The session traffic might have been identified with different methods to recognize and characterize the session. In one first embodiment the session is characterized by means of the packet headers of the packets of a session. In a second embodiment, the session is recognized and characterized by means of the end-to-end signaling messages in connection with the forming of a logical link for the connection. In a third embodiment, the session is recognized and characterized by means of direct signaling messages to the apparatus of the invention.
The radio access bearer attributes consist of the quality of service and bandwidth request, which in turn are based on local static conversion database, remote conversion database, user profile and /or load indicators from bearer management.
In one embodiment of the invention, changes are recognized during an on-going session, as a result of which the radio access bearer attributes are changed. The changes might be recognized so that the session is probed periodically in order to recognize changes in the application needs by any combination of the above methods of starting session flows. In one preferred embodiment, back pressure mechanisms are used to go back to the application in case of varying conditions on the radio interface, e.g. suddenly available more spectrum or worsening conditions due to bad radio conditions or congestions. The invention can be used for monitoring the traffic on an already established radio access bearer and possibly be used to adjust the bearer characteristics through radio access bearer service (RABS) re-negotiation.
The changes to be made in the radio access bearer attributes during an ongoing session can be carried out through many different re-negotiation sequences and are explained later in this text.
Thus, in the invention, the radio access bearers are granted, on the border between the core network and the radio access network, on the basis of a service negotiation that uses radio access bearer service attributes. These attributes characterize the radio access bearer services and the intention is not only to offer the bearer with the right quality of service but also to enable efficient algorithms for radio resource management. One example of the latter is the admission control algorithms which can take advantage of the knowledge about the exact application needs by granting radio access to as many mobile users as possible.
By the apparatus and methods of the invention it is possible to perform radio access negotiation for packet data based cellular systems where no obvious connections exist on the network communication level, i.e. when using IP network protocol. The proposed introduction of a logical node on the core network side, or alternatively, on the radio access network side, together with the methods for recognizing the application needs in terms of Quality of Service, provides means for efficient Radio Access Bearer Service (RABS) negotiation. Consequently, by allocating adequate RABS, it is much easier to develop admission control algorithms for spectrum efficient utilization of scarce radio resources. Further, the combination of said node and the usage of traffic recognition methods makes it possible to map the incoming packet data traffic on the right radio access bearer.
Some embodiments of the invention are described in the following by means of figures and a flow scheme. The invention is not restricted to the details of the following presentation as the invention can vary within the scope of the claims.